Groups > sci.electronics.design > #460378

Re: Fast buffer idea

Subject	Re: Fast buffer idea
Newsgroups	sci.electronics.design
References	(6 earlier) <EEiSA.74451$bl5.68044@fx25.iad> <IMiSA.118013$ef.91898@fx34.iad> <XnsA7767E5052407idtokenpost@69.16.179.22> <ofcldu$n1m$1@gioia.aioe.org> <XnsA776875EB8A7idtokenpost@69.16.179.23>
From	bitrex <bitrex@de.lete.earthlink.net>
Message-ID	<MAlSA.118066$ef.9536@fx34.iad> (permalink)
Organization	frugalusenet - www.frugalusenet.com
Date	2017-05-15 13:30 -0400

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On 05/15/2017 01:18 PM, Steve Wilson wrote:
> Jan Panteltje <pNa0nStpealmtje@yahoo.com> wrote:
>
>> On a sunny day (Mon, 15 May 2017 16:24:56 GMT) it happened Steve
>> Wilson <no@spam.com> wrote in
>> <XnsA7767E5052407idtokenpost@69.16.179.22>:
>>
>>> bitrex <bitrex@de.lete.earthlink.net> wrote:
>>>
>>>> On 05/15/2017 10:09 AM, bitrex wrote:
>>>>> On 05/15/2017 10:01 AM, John Larkin wrote:
>>>>>
>>>>>> BW is 230 MHz as a unity-gain buffer. Each half of the dual will
>>>>>> source and sink 88 mA. And there are lots of faster THS-series
>>>>>> parts.
>>>>>>
>>>>>>>
>>>>>>> But indeed you can do that with a few NPNs of the old days,
>>>>>>>
>>>>>>
>>>>>> Post it.
>>>>>
>>>>> With discretes you can have:
>>>>>
>>>>> 1) wide bandwidth
>>>>>
>>>>> 2) low parts count
>>>>>
>>>>> 3) low quiescent current draw
>>>>>
>>>>> Pick two.
>>>>
>>>> The two transistor circuit Jan posted does have a pretty wide
>>>> bandwidth and a low parts count. It has a pretty nice small signal
>>>> output impedance, but its large-signal output impedance is bad. It
>>>> also draws a  relatively large amount of quiescent current.
>>>
>>> I somehow missed the two transistor circuit that Jan posted. Can you
>>> please repost the link?
>>>
>>> Thanks
>>
>> From:
>>  http://panteltje.com/panteltje/quadcopter/hud.html
>>  the circuit diagram:
>>   http://panteltje.com/panteltje/quadcopter/hud-0.1_circuit_diagram_IMG
>>   _5984.JPG bottom left:
>> that has a gain of 2, so can drive a 75 Ohm cable with reasonable Zi.
>> The DC path requires an other 75 Ohm at the end of the cable.
>
> OK, thanks.
>
> That is a Sziklai Pair with a voltage divider in the feedback path:
>
>   https://en.wikipedia.org/wiki/Sziklai_pair
>
> It would normally have the same thermal drift as a simple base-emitter
> junction, but the divide by two may increase it.
>
> The output impedance may be increased due to the low loop gain. The
> bandwidth is determined by the transistors you use.

Its output impedance for large negative-going signals is _dogshit_, 
regardless of what the small-signal analysis feedback-loop-gain etc. 
calculations indicate. It can source current okay. It definitely can't 
sink it.

It doesn't really matter for a composite video signal, though, because 
it's not really that wide a bandwidth signal. The only potentially 
difficult fast full-level transition I think of would be if you have to 
go from the "back porch" immediately to "full luminance."

Thread

Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 13:50 -0400
  Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 11:27 -0700
    Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-14 19:19 +0000
      Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 15:24 -0400
      Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 12:54 -0700
        Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:02 -0400
          Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 13:10 -0700
            Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:16 -0400
              Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:18 -0400
              Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 14:14 -0700
              Re: Fast buffer idea "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-05-15 19:51 +0100
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 13:17 -0700
                Re: Fast buffer idea Clifford Heath <clifford.heath@gmail.com> - 2017-05-17 09:14 +1000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-16 16:26 -0700
                Re: Fast buffer idea "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-17 02:04 -0500
        Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-14 20:26 +0000
          Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:31 -0400
          Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:43 -0400
          Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 14:17 -0700
            Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-14 21:53 +0000
              Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 16:14 -0700
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 19:59 -0400
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 20:06 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 00:16 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 20:10 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 03:28 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 20:48 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 04:17 +0000
        Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 07:56 +0000
          Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 06:58 -0400
            Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 12:59 +0000
          Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-15 07:01 -0700
            Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 10:09 -0400
              Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 10:18 -0400
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-15 08:56 -0700
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 16:02 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 10:33 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 18:15 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 14:25 -0400
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 14:26 -0400
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 16:24 +0000
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 16:36 +0000
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 17:18 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 13:30 -0400
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 18:07 +0000
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 19:19 +0000
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 19:45 +0000
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-16 08:33 +0000
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 19:13 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 15:33 -0400
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-16 08:16 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-16 22:10 -0400
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 19:10 +0000
              Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-15 08:55 -0700
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 12:51 -0400
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 12:56 -0400
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 13:05 -0400
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 10:28 -0700
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 13:38 -0400
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 11:29 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 18:41 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 13:19 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 20:46 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 13:56 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 21:00 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 16:46 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-16 01:22 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-16 11:16 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-16 18:55 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-16 12:21 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-16 20:33 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-16 14:00 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-16 21:21 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-16 16:15 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-16 23:58 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-16 17:51 -0700
                Re: Fast buffer idea pcdhobbs@gmail.com - 2017-05-16 16:30 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-17 00:16 +0000
                Re: Fast buffer idea pcdhobbs@gmail.com - 2017-05-16 18:05 -0700
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-16 20:05 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-25 01:13 +0000
                Re: Fast buffer idea Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-24 21:43 -0400
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-30 03:16 +0000
                Re: Fast buffer idea Ralph Barone <ralph@invalid.com> - 2017-05-17 02:26 +0000
                Re: Fast buffer idea Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-05-17 08:34 +0200
                Re: Fast buffer idea Ralph Barone <ralph@invalid.com> - 2017-05-17 14:31 +0000
                Re: Fast buffer idea Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-17 10:39 -0400
                Re: Fast buffer idea Reinhardt Behm <rbehm@hushmail.com> - 2017-05-17 23:02 +0800
                Re: Fast buffer idea Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-05-16 21:24 +0200
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-16 20:12 -0700
                Re: Fast buffer idea Winfield Hill <hill@rowland.harvard.edu> - 2017-05-25 04:38 -0700
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-25 07:28 -0700
                Re: Fast buffer idea "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-26 08:54 -0500
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-26 14:14 +0000
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-26 07:21 -0700
                Re: Fast buffer idea "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-05-16 20:27 +0100
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 15:05 -0400
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 15:19 -0400
                Re: Fast buffer idea John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-15 13:21 -0700
                Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 20:56 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 17:37 -0400
              Re: Fast buffer idea "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-05-15 19:50 +0100
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 19:25 +0000
                Re: Fast buffer idea "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-05-16 20:19 +0100
            Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 14:33 +0000
              Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 13:15 -0400
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-15 19:05 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-15 15:38 -0400
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-16 08:12 +0000
                Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-16 18:47 +0000
                Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-16 21:52 -0400
                Re: Fast buffer idea Winfield Hill <hill@rowland.harvard.edu> - 2017-05-25 05:05 -0700
                Re: Fast buffer idea pcdhobbs@gmail.com - 2017-05-25 05:42 -0700
                Re: Fast buffer idea Winfield Hill <hill@rowland.harvard.edu> - 2017-05-25 05:49 -0700
                Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-25 08:10 -0700
                Re: Fast buffer idea Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-05-25 15:01 +0200
      Re: Fast buffer idea "John Miles, KE5FX" <jmiles@gmail.com> - 2017-05-14 18:53 -0700
        Re: Fast buffer idea Steve Wilson <no@spam.com> - 2017-05-15 02:45 +0000
    Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 15:23 -0400
  Re: Fast buffer idea "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-05-14 20:28 +0100
    Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:00 -0400
    Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 16:10 -0400
      Re: Fast buffer idea Winfield Hill <hill@rowland.harvard.edu> - 2017-05-14 17:58 -0700
        Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-14 23:13 -0400
        Re: Fast buffer idea Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-05-16 17:27 -0700
          Re: Fast buffer idea Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-05-16 17:34 -0700
      Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-14 20:14 -0700
        Re: Fast buffer idea "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-05-15 19:42 +0100
  Re: Fast buffer idea "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-16 03:29 -0500
    Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-16 06:57 -0700
      Re: Fast buffer idea bitrex <bitrex@de.lete.earthlink.net> - 2017-05-16 22:47 -0400
        Re: Fast buffer idea John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-16 20:18 -0700
          Re: Fast buffer idea "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-17 02:22 -0500
    Re: Fast buffer idea Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-16 14:05 +0000

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